Fabric properties measurements using real-time sewing machine motor current signature

Abstract

This work is aiming to develop a new feature to be added to the state-of-the-art sewing machines by studying the effect of the needle penetration force on the motor current. A real-time variant current drawn by the motor is recorded at a sampling rate of 3.125 kS/s. The time signal is transformed into frequency spectrum that has peaks at specific frequencies related to needle penetrating fabrics.The proposed technique can mark out different denim fabric properties, mainly the fabric type and thickness. Increasing the fabric weight from 302.7 to 463.73 g/m2 and thickness from 1 to 8 plies appear as a linear shift in the frequency peaks towards lower values within a range of frequencies between 1170 and 1300 Hz. The frequency shifts by almost −1 Hz for every 20 g/m2 increase in the fabric weight while it shifts by almost −11 Hz per fabric ply increment. The correlation coefficient between the frequency shift and the number of fabric plies is calculated to be 0.998. On the other hand, frequency shifts toward higher frequency values by up to +52 Hz when different chemical treatments are applied to the fabric samples. The measured data is verified by comparing them to similar data obtained using L&M. The results of these two measurements were highly correlated with correlation coefficients of up to 0.91. The obtained results nominates that the proposed technique can be used as a real-time fabric detector for sewing machines.